Selective deposition of carbon on photoresist layer for lithography applications

ABSTRACT

A method for etching a hardmask layer includes forming a photoresist layer comprising an organometallic material on a hardmask layer comprising a metal-containing material, exposing the photoresist layer to ultraviolet radiation through a mask having a selected pattern, removing un-irradiated areas of the photoresist layer to pattern the photoresist layer, forming a passivation layer comprising a carbon-containing material selectively on a top surface of the patterned photoresist layer, and etching the hardmask layer exposed by the patterned photoresist layer having the passivation layer formed thereon.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 63/023,290, filed May 12, 2020, which is herein incorporated byreference.

BACKGROUND Field

The embodiments herein generally relate to a film stack and an etchingprocess for etching such film stack with high selectivity and goodprofile control to extreme ultraviolet (EUV) lithography exposure andpatterning process.

Description of the Related Art

Reliably producing submicron and smaller features is one of the keyrequirements of very large scale integration (VLSI) and ultra largescale integration (ULSI) of semiconductor devices. However, with thecontinued miniaturization of circuit technology, the size and pitch ofcircuit features, such as interconnects, have placed additional demandson processing capabilities. The multilevel interconnects that lie at theheart of this technology require precise imaging and placement of highaspect ratio features, such as vias and other interconnects. Reliableformation of these interconnects is critical to further increases indevice and interconnect density. Additionally, forming sub-micron sizefeatures and interconnects with reduced waste of intermediate materials,such as resists and hardmask materials, is desired.

As feature sizes have become smaller, the demand for higher aspectratios, defined as the ratio between the depth of the feature and thewidth of the feature, has steadily increased to 20:1 and even greater.Developing film stacks and etch processes that are capable of reliablyforming features with such high aspect ratios presents a significantchallenge. However, inaccurate control or low resolution of thelithography exposure and developing process may cause inaccuratedimension of a photoresist layer utilized to transfer features in a filmstack, resulting in unacceptable line width roughness (LWR). Large linewidth roughness (LWR) and undesired wiggling profile of the photoresistlayer resulting from the lithography exposure and developing process maycause inaccurate feature transfer to the film stack, thus, eventuallyleading to device failure and yield loss.

Furthermore, during etching of a film stack, redeposition or build-up ofby-products or other materials generated during the etching process mayaccumulate on the top and/or sidewalls of the features being etched,thus undesirably blocking the opening of the feature being formed in thematerial layer. Different materials selected for the film stack mayresult in different amounts or profiles of the by-products redepositedin the film stack. Furthermore, as the opening of the etched featuresare narrowed and/or sealed by the accumulated redeposition of material,the reactive etchants are prevented from reaching the lower surface ofthe features, thus limiting the aspect ratio that may be obtained.Additionally, as the redeposition material or build-up of by-productsmay randomly and/or irregularly adhere to the top surface and/orsidewalls of the features being etched, the resulting irregular profileand growth of the redeposition material may alter the flow path of thereactive etchants, thus resulting in bowing or twisting profiles of thefeatures formed in the material layer. Inaccurate profile or structuraldimensions may result in collapse of the device structure, eventuallyleading to device failure and low product yield. Poor etchingselectivity to the materials included in the film stack may undesirablyresult in an inaccurate profile control, thus eventually leading todevice failure.

Therefore, there is a need in the art for a proper film stack and anetching method for etching features with desired profile and smalldimensions in such film stack.

SUMMARY

Methods for forming a film stack and etching the same to form highaspect ratio features in the film stack are provided. The methodsdescribed herein facilitate profile and dimension control of featureswith high aspect ratios through a proper sidewall and bottom managementscheme with desired materials selected for the film stack. In one ormore embodiments, a method for etching a hardmask layer includes forminga photoresist layer comprising an organometallic material on a hardmasklayer comprising a metal-containing material, exposing the photoresistlayer to ultraviolet radiation through a mask having a selected pattern,removing un-irradiated areas of the photoresist layer to pattern thephotoresist layer, forming a passivation layer comprising acarbon-containing material selectively on a top surface of the patternedphotoresist layer, and etching the hardmask layer exposed by thepatterned photoresist layer having the passivation layer formed thereon.

In other embodiments, a method for etching a film stack includes forminga bottom anti-reflective coating layer on a film stack, forming ahardmask layer comprising a metal-containing material on the bottomanti-reflective coating layer, forming a photoresist layer comprising anorganometallic material on the hardmask layer, exposing the photoresistlayer to ultraviolet radiation through a mask having a selected pattern,removing un-irradiated areas of the photoresist layer to pattern thephotoresist layer, forming a passivation layer comprising acarbon-containing material selectively on a top surface of the patternedphotoresist layer, etching the hardmask layer exposed by the patternedphotoresist layer having the passivation layer formed thereon to patternthe hardmask layer, etching the bottom anti-reflective coating layerexposed by the patterned hardmask layer to pattern the bottomanti-reflective coating layer, and etching the film stack exposed by thepatterned bottom anti-reflective coating layer.

In some embodiments, a method for selectively forming a passivationlayer on a patterned photoresist layer includes exposing a photoresistlayer comprising an organometallic material to ultraviolet radiationthrough a mask, removing un-irradiated areas of the photoresist layer,and forming a passivation layer comprising a carbon-containing materialselectively on a top surface of the photoresist layer.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of theembodiments herein are attained and can be understood in detail, a moreparticular description of the disclosure, briefly summarized above, maybe had by reference to the examples thereof which are illustrated in theappended drawings.

FIG. 1 is a cross-sectional view of a processing chamber according toone embodiment.

FIG. 2 depicts a flow diagram for a patterning process according to oneembodiment.

FIGS. 3A, 3B, 3C, 3D, 3E, 3F, 3G, 3H, and 3I are cross-sectional viewsof a structure formed during the patterning process depicted in FIG. 2according to one embodiment.

To facilitate understanding of the embodiments, identical referencenumerals have been used, where possible, to designate identical elementsthat are common to the figures. It is contemplated that elements andfeatures of one embodiment may be beneficially incorporated in otherembodiments without further recitation.

It is to be noted, however, that the appended drawings illustrate onlyexemplary examples and are therefore not to be considered limiting ofits scope, for the invention may admit to other equally effectiveembodiments.

DETAILED DESCRIPTION

Methods for forming a film stack and etching the same to form highaspect ratio features in the film stack are provided. The methodsdescribed herein facilitate profile and dimension control of featureswith high aspect ratios through a proper sidewall and bottom managementscheme with desired materials selected for the film stack. Inparticular, the methods described herein provide a metal-containingphotoresist layer having a carbon-containing passivation layerselectively disposed thereon that has a high etch selectivity from anunderlying metal-containing hardmask layer, leading to higher accuracycontrol of profile of openings etched in the hardmask layer.

FIG. 1 is a cross-sectional view of one example of a processing chamber100 suitable for performing a patterning process to etch a film stackhaving a hardmask layer fabricated from a metal-containing material.Suitable processing chambers that may be adapted for use with theteachings disclosed herein include, for example, an ENABLER® or C3®processing chamber available from Applied Materials, Inc. of SantaClara, Calif. Although the processing chamber 100 is shown including aplurality of features that enable superior etching performance, it iscontemplated that other processing chambers may be adapted to benefitfrom one or more of the inventive features disclosed herein.

The processing chamber 100 includes a chamber body 102 and a lid 104which enclose an interior volume 106. The chamber body 102 is typicallyfabricated from aluminum, stainless steel or other suitable material.The chamber body 102 generally includes sidewalls 108 and a bottom 110.A substrate support pedestal access port (not shown) is generallydefined in a sidewall 108 and a selectively sealed by a slit valve tofacilitate entry and egress of a substrate 103 from the processingchamber 100. An exhaust port 126 is defined in the chamber body 102 andcouples the interior volume 106 to a pump system 128. The pump system128 generally includes one or more pumps and throttle valves utilized toevacuate and regulate the pressure of the interior volume 106 of theprocessing chamber 100. In one or more implementations, the pump system128 maintains the pressure inside the interior volume 106 at operatingpressures typically between about 10 mTorr to about 500 Torr.

The lid 104 is sealingly supported on the sidewall 108 of the chamberbody 102. The lid 104 may be opened to allow excess to the interiorvolume 106 of the processing chamber 100. The lid 104 includes a window142 that facilitates optical process monitoring. In one implementation,the window 142 is comprised of quartz or other suitable material that istransmissive to a signal utilized by an optical monitoring system 140mounted outside the processing chamber 100.

The optical monitoring system 140 is positioned to view at least one ofthe interior volume 106 of the chamber body 102 and/or a substrate 103positioned on a substrate support pedestal assembly 148 through thewindow 142. In one or more embodiments, the optical monitoring system140 is coupled to the lid 104 and facilitates an integrated depositionprocess that uses optical metrology to provide information that enablesprocess adjustment to compensate for incoming substrate pattern featureinconsistencies (such as thickness, and the like), provide process statemonitoring (such as plasma monitoring, temperature monitoring, and thelike) as needed. One optical monitoring system that may be adapted tobenefit from the invention is the EyeD® full-spectrum, interferometricmetrology module, available from Applied Materials, Inc., of SantaClara, Calif.

A gas panel 158 is coupled to the processing chamber 100 to provideprocess and/or cleaning gases to the interior volume 106. In the exampledepicted in FIG. 1, inlet ports 132′, 132″ are provided in the lid 104to allow gases to be delivered from the gas panel 158 to the interiorvolume 106 of the processing chamber 100.

A showerhead assembly 130 is coupled to an interior surface 114 of thelid 104. The showerhead assembly 130 includes a plurality of aperturesthat allow the gases flowing through the showerhead assembly 130 fromthe inlet ports 132′, 132″ into the interior volume 106 of theprocessing chamber 100 in a predefined distribution across the surfaceof the substrate 103 being processed in the processing chamber 100.

A remote plasma source 177 may be optionally coupled to the gas panel158 to facilitate dissociating gas mixture from a remote plasma prior toentering into the interior volume 106 for processing. A radio frequency(RF) power source 143 is coupled through a matching network 141 to theshowerhead assembly 130. The RF power source 143 typically is capable ofproducing up to about 3,000 W at a tunable frequency in a range fromabout 50 kHz to about 200 MHz.

The showerhead assembly 130 additionally includes a region transmissiveto an optical metrology signal. The optically transmissive region orpassage 138 is suitable for allowing the optical monitoring system 140to view the interior volume 106 and/or the substrate 103 positioned onthe substrate support pedestal assembly 148. The passage 138 may be anaperture or plurality of apertures formed or disposed in the showerheadassembly 130 that is substantially transmissive to the wavelengths ofenergy generated by, and reflected back to, the optical monitoringsystem 140. In one or more embodiments, the passage 138 includes thewindow 142 to prevent gas leakage through the passage 138. The window142 may be a sapphire plate, quartz plate or other suitable material.The window 142 may alternatively be disposed in the lid 104.

In one implementation, the showerhead assembly 130 is configured with aplurality of zones that allow for separate control of gas flowing intothe interior volume 106 of the processing chamber 100. In the exampleillustrated in FIG. 1, the showerhead assembly 130 as an inner zone 134and an outer zone 136 that are separately coupled to the gas panel 158through separate inlet ports 132′, 132″.

The substrate support pedestal assembly 148 is disposed in the interiorvolume 106 of the processing chamber 100 below the showerhead assembly130. The substrate support pedestal assembly 148 holds the substrate 103during processing. The substrate support pedestal assembly 148 generallyincludes a plurality of lift pins (not shown) disposed therethrough thatare configured to lift the substrate 103 from the substrate supportpedestal assembly 148 and facilitate exchange of the substrate 103 witha robot (not shown) in a conventional manner. An inner liner 118 mayclosely circumscribe the periphery of the substrate support pedestalassembly 148.

In one implementation, the substrate support pedestal assembly 148includes a mounting plate 162, a base 164 and an electrostatic chuck166. The mounting plate 162 is coupled to the bottom 110 of the chamberbody 102 and includes passages for routing utilities, such as fluids,power lines and sensor leads, among others, to the base 164 and theelectrostatic chuck 166. The electrostatic chuck 166 includes at leastone clamping electrode 180 for retaining the substrate 103 belowshowerhead assembly 130. The electrostatic chuck 166 is driven by achucking power source 182 to develop an electrostatic force that holdsthe substrate 103 to the chuck surface, as is conventionally known.Alternatively, the substrate 103 may be retained to the substratesupport pedestal assembly 148 by clamping, vacuum, or gravity.

At least one of the base 164 or electrostatic chuck 166 may include atleast one optional embedded heater 176, at least one optional embeddedisolator 174, and a plurality of conduits 168, 170 to control thelateral temperature profile of the substrate support pedestal assembly148. The conduits 168, 170 are fluidly coupled to a fluid source 172that circulates a temperature regulating fluid therethrough. The heater176 is regulated by a power source 178. The conduits 168, 170 and heater176 are utilized to control the temperature of the base 164, therebyheating and/or cooling the electrostatic chuck 166 and ultimately, thetemperature profile of the substrate 103 disposed thereon. Thetemperature of the electrostatic chuck 166 and the base 164 may bemonitored using a plurality of temperature sensors 190, 192. Theelectrostatic chuck 166 may further comprise a plurality of gas passages(not shown), such as grooves, that are formed in a substrate supportpedestal supporting surface of the electrostatic chuck 166 and fluidlycoupled to a source of a heat transfer (or backside) gas, such as He. Inoperation, the backside gas is provided at controlled pressure into thegas passages to enhance the heat transfer between the electrostaticchuck 166 and the substrate 103.

In one implementation, the substrate support pedestal assembly 148 isconfigured as a cathode and includes a clamping electrode 180 that iscoupled to a plurality of RF bias power sources 184, 186. The RF biaspower sources 184, 186 are coupled between the electrode 180 disposed inthe substrate support pedestal assembly 148 and another electrode, suchas the showerhead assembly 130 or the lid 104 of the chamber body 102.The RF bias power excites and sustains a plasma discharge formed fromthe gases disposed in the processing region of the chamber body 102.

In the example depicted in FIG. 1, the dual RF bias power sources 184,186 are coupled to the electrode 180 disposed in the substrate supportpedestal assembly 148 through a matching circuit 188. The signalgenerated by the RF bias power sources 184, 186 is delivered throughmatching circuit 188 to the substrate support pedestal assembly 148through a single feed to ionize the gas mixture provided in theprocessing chamber 100, thereby providing ion energy necessary forperforming a deposition or other plasma enhanced process. The RF biaspower sources 184, 186 are generally capable of producing an RF signalhaving a frequency of about 50 kHz to about 200 MHz and a power of about0 watts and about 8,000 watts, such as about 1 watt and about 5,000watts. An additional bias power source 189 may be coupled to theelectrode 180 to control the characteristics of the plasma.

During operation, the substrate 103 is disposed on the substrate supportpedestal assembly 148 in the processing chamber 100. A process gasand/or gas mixture is introduced into the chamber body 102 through theshowerhead assembly 130 from the gas panel 158. The pump system 128maintains the pressure inside the chamber body 102 while removingdeposition by-products.

A controller 150 is coupled to the processing chamber 100 to controloperation of the processing chamber 100. The controller 150 includes acentral processing unit (CPU) 152, a memory 154, and a support circuit156 utilized to control the process sequence and regulate the gas flowsfrom the gas panel 158. The CPU 152 may be any form of general purposecomputer processor that may be used in an industrial setting. Thesoftware routines can be stored in the memory 154, such as random accessmemory, read only memory, floppy, or hard disk drive, or other form ofdigital storage. The support circuit 156 is conventionally coupled tothe CPU 152 and may include cache, clock circuits, input/output systems,power supplies, and the like. Bi-directional communications between thecontroller 150 and the various components of the processing chamber 100are handled through numerous signal cables.

FIG. 2 is a flow diagram of a method 200 for a patterning processaccording to one embodiment described herein. FIGS. 3A-3I arecross-sectional views of a structure 300 formed during the patterningprocess of FIG. 2. The method 200 may be utilized to form features, suchas trenches, vias, openings, and the like, with desired criticaldimensions and profiles. In some embodiments, dimensions of suchfeatures are between about 14 nm and about 22 nm, for example about 18nm. The structure 300 may be utilized in a gate structure, a contactstructure or an interconnection structure in a front end or back endprocess. Alternatively, the method 200 may be beneficially utilized toetch other types of structures. Those skilled in the art shouldrecognize that a full process for forming a semiconductor device and theassociated structures are not illustrated in the drawings or describedherein. Although various operations are illustrated in the drawings anddescribed herein, no limitation regarding the order of such operationsor the presence or absence of operations is implied. Operations depictedor described as sequential are, unless explicitly specified, merely doneso for purposes of explanation without precluding the possibility thatthe respective operations are actually performed in concurrent oroverlapping manner, at least partially if not entirely.

The method 200 starts at operation 210 by transferring or providing afilm stack 302, as shown in FIG. 3A, in a processing chamber, such asthe processing chamber 100 depicted in FIG. 1. In one embodiment, thefilm stack 302 may have a number of layers vertically stacked on asubstrate. The film stack 302 may include one or more metal-containingdielectric layers and one or more silicon-containing dielectric layers.In some embodiments, the metal-containing dielectric layers may beformed of a high-k material having a dielectric constant greater than 4.Suitable examples of the high-k materials include aluminum oxide(Al₂O₃), tantalum oxide (Ta₂O₅), tantalum nitride (TaN), tantalumoxynitride (TaN_(x)O_(y), 0≤x, y≤1), titanium oxide (TiO₂), titaniumnitride (TiN), zirconium dioxide (ZrO₂), hafnium dioxide (HfO₂), hafniumsilicon oxide (HfSiO₄), lanthanum oxide (La₂O₃), yttrium oxide (Y₂O₃),strontium titanate (SrTiO₃), barium strontium titanate (BST, BaSrTiO₃),bismuth doped strontium titanate (Bi:SrTiO₃), and lead zirconatetitanate (PZT, Pb[Zr_(x)Ti_(1-x)]O₃, 0≤x≤1), among others. Thesilicon-containing dielectric layers may be formed of silicon oxide(SiO₂), silicon nitride (SiN), silicon oxynitride (SiON), siliconcarbide (SiC), silicon oxycarbide (SiO_(x)C_(y), 0≤x, y≤1), or the like.

The substrate may be any one of semiconductor substrates, siliconwafers, glass substrates and the like. The substrate may be formed of amaterial such as crystalline silicon (e.g., Si<100> or Si<111>), siliconoxide, strained silicon, silicon germanium, germanium, doped or undopedpolysilicon, doped or undoped silicon wafers and patterned ornon-patterned wafers silicon on insulator (SOI), carbon doped siliconoxides, silicon nitride, doped silicon, germanium, gallium arsenide,glass, or sapphire. The substrate may have various dimensions, such as200 mm, 300 mm, 450 mm, or other diameter, as well as being arectangular or square panel.

At operation 220, a bottom anti-reflective coating (BARC) layer 304 isformed on the film stack 302, as depicted in FIG. 3A. In someembodiments, the BARC layer 304 is made of carbon-containing material,such as boron doped amorphous carbon. The BARC layer 304 may be aSaphira™ Advanced Patterning Film (APF) carbon hardmask produced byApplied Materials, Inc., located in Santa Clara, Calif. In someembodiments, the BARC layer 304 is a high-density carbon-containinglayer and has superior film qualities such as improved hardness anddensity. Such hardness and density allow the BARC layer 304 to act as astronger barrier against metal infiltration and to prevent and reducenanofailures to a greater extent than conventional spin-on carbon (SOC)hard masks.

The BARC layer 304 may be formed by a physical vapor deposition (PVD)process, a plasma enhanced chemical vapor deposition (PECVD) process, orother suitable deposition processes. In one embodiment, the BARC layer304 is a diamond-like carbon layer formed by chemical vapor depositionCVD (plasma enhanced and/or thermal) processes usinghydrocarbon-containing gas mixtures including precursors such as C₂H₂,C₃H₆, CH₄, C₄H₈, 1,3-dimethyladamantane, bicyclo[2.2.1]hepta-2,5-diene(2,5-Norbornadiene), adamantine (C₁₀H₁₆), norbornene (C₇H₁₀), orcombinations thereof. The deposition process may be carried out attemperatures ranging from −50 degrees Celsius to 600 degrees Celsius.The deposition process may be carried out at pressures ranging from 0.1mTorr to 10 Torr in the interior volume 106 of the processing chamber100. The hydrocarbon-containing gas mixture may further include acarrier gas such as He, Ar, Xe, N₂, H₂, or combination thereof, andetchant gases such as Cl₂, CF₄, NF₃, or combination thereof to improvefilm quality. The plasma (e.g., capacitive-coupled plasma) may be formedfrom either top and bottom electrodes or side electrodes of theprocessing chamber 100. The electrodes may be formed from a singlepowered electrode, dual powered electrodes, or more electrodes withmultiple frequencies such as, but not limited to, 350 KHz, 2 MHz, 13.56MHz, 27 MHz, 40 MHz, 60 MHz, and 100 MHz, being used alternatively orsimultaneously in a CVD system.

At operation 230, a hardmask layer 306 is formed on the BARC layer 304,as depicted in FIG. 3B. The hardmask layer 306 may be a metal oxidelayer. Material selected for the hardmask layer 306 may affectreflection and/or absorption efficiency of extreme ultraviolet (EUV)radiation having a wavelength of between about 5 nm and about 20 nm, forexample, about 13.5 nm during lithography exposure process. Thus, byproper selection of material for the hardmask layer 306, performance ofEUV lithography exposure process, such as high lithography resolution,defect reduction, photoresist layer profile control, energy dosereduction, and/or line edge roughness reduction, may be enhanced. Forexample, material having a higher metal concentration may provide ahigher absorption coefficient of EUV radiation, and thus the hardmasklayer 306 may be formed of metal-containing material, such as a metaldielectric layer, containing one or more metal elements having an atomicnumber greater than 28, such as 29-32, 37-51, and 55-83. Suitable metalelements include tin (Sn), tantalum (Ta), indium (In), gallium (Ga),zinc (Zn), zirconium (Zr), aluminum (Al), or combinations thereof.Furthermore, low concentration of silicon dopants and/or oxygen elementsin the metal-containing material may further increase free carriers,enhancing absorption coefficient of EUV radiation and reducinglikelihood of defect generation. Suitable examples of themetal-containing materials for the hardmask layer 306 may be or includetin oxide (SnO), tin silicon oxide (SnSiO), tantalum oxide (TaO), indiumtin oxide (InSnO), indium gallium zinc oxide (IGZO), one or more alloysthereof, one or more dopants thereof, or any combination thereof havinga ratio of metal elements to silicon or oxygen elements (metal:Si/O)between about 80:1/19 and about 90:1/9. The metal-containing materialfor the hardmask layer 306 may have a EUV absorption cross sectiongreater than 1×10⁵ (cm²/mol) under an EUV radiation having a wavelengthranging between about 5 nm and about 20 nm. In one or more examples, thehardmask layer 306 has a thickness between about 10 Å and about 500 Å,such as between about 20 Å and about 200 Å, for example, between about50 Å and about 100 Å.

In some embodiments, the hardmask layer 306 includes multiple layers.The hardmask layer 306 may have multiple layers that are formed fromdifferent metal-containing materials. Selection of the metal-containingmaterials for the multiple layers is based on different absorptioncoefficients of the metal-containing materials. For example, multiplelayers having high to low, low to high, or alternating high and lowabsorption coefficients may be sequentially formed so as to enhancereflection of the EUV radiation during the lithography exposure process.In one or more examples, the metal elements selected for one of multiplelayers may have atomic numbers greater than 28, such as greater than 35and another may have atomic numbers less than 28.

In some embodiments, the hardmask layer 306 includes a bilayerstructure, having a first portion (e.g., an upper portion or layer)containing a metal element having an atomic number greater than 28, suchas 29-32, 37-51, and 55-83, and a second portion (e.g., a lower portionor layer) containing an element having an atomic number of less than 28,such as 3-8, 11-16, and 19-27.

In some embodiments, the hardmask is formed as a gradient havingdifferent ratio of the metal elements to the silicon and/or oxygenelements in the hardmask layer 306 to provide different absorptioncoefficients along the bulk film body of the hardmask layer 306. Forexample, the metal element concentration of the hardmask layer 306 maybe gradually increased or decreased with the thickness increase of thehardmask layer 306. Alternatively, each layer of the bilayer structureor the multiple layers of the hardmask layer 306 may also be a gradientlayer. For example, in the bilayer structure of the hardmask layer 306,the upper portion of the hardmask layer 306 may have a low resistivitywith relatively high metal element concentration or even pure metallayer (e.g., such as a metallic Sn layer) while the lower portion of thehardmask layer 306 may have a high concentration of silicon and/oroxygen.

The hardmask layer 306 may be formed by a CVD process, a PVD process, anatomic layer deposition (ALD) process, a spin-on-coating process, aspray coating process, or other suitable deposition processes. In someembodiments, during a plasma enhanced CVD or PVD process of forming thehardmask layer 306, a carrier gas and/or an inert gas with relativelyhigher atomic weight, such as Xe or Kr, may be used. The temperaturecontrolled during the formation of the hardmask layer 306 may becontrolled between −50° C. and about 250° C. It is believed that arelatively low temperature control, e.g., less than 250° C., whileforming the hardmask layer 306 may assist forming the hardmask layer 306at a relatively slow deposition rate, rendering a film surface with arelatively smooth surface.

At operation 240, a photoresist layer 308 is formed on the hardmasklayer 306, as depicted in FIG. 3C. In the embodiments described herein,the photoresist layer 308 is formed of an organometallic materialincluding organic ligands. The organometallic material layer may beformed of a polymeric metal oxo/hydroxo network in which the metals arebonded with the oxo ligands (O²⁻) and hydroxo ligands (OH⁻), and alsowith organic ligands, or a polynuclear metal oxo/hydroxo species withorganic ligands.

The photoresist layer 308 may be formed by a CVD process, a PVD process,an ALD process, a spin-on-coating process, a spray coating process, orother suitable deposition processes, using a precursor solution thatincludes metal oxo-hydroxo cations with organic ligands in an organicsolvent. Metal (M) oxo-hydroxo cations herein refer to one or more metal(M) ions that are bonded to oxygen atoms (0) to form oxo ligands (O²⁻)and/or hydroxo ligands (OH⁻) with release of hydrogen ions (H⁻) in anaqueous solutions. Metal (M) oxo-hydroxo cations are further bonded tothe organic ligands to form one or more metal carbon (M-C) ligand bondsand/or metal carboxylate (M-O₂C) ligand bonds. Suitable metals (M) forformation of metal oxo/hydroxo cations include group 13, 14, and 15metals, such as tin (Sn), antimony (Sb), and indium (In). Additionalmetals, for example, Ti, Zr, Hf, V, Co, Mo, W, Al, Ga, Si, Ge, P, As, Y,La, Ce, Lu, or combinations thereof, may be blended in the precursorsolution to produce more complex polynuclear metal oxo/hydroxo cations(i.e., including two or more metal atoms). The additional metals may beas alternatives to or in addition to tin (Sn), antimony (Sb), and/orindium (In). If blends of metal ions are used, the mole ratio ofnon-tin/antimony/indium ion per tin/antimony/indium metal ion is up toabout 1 in one example, and between about 0.1 and about 0.75 in otherexamples. In some embodiments, tin (Sn) or indium (In) is used in theprecursor solution to form a photoresist layer having strong absorptionof extreme ultraviolet radiation (EUV) at 13.5 nm wavelength, and incombination with organic ligands, good absorption of ultraviolet (UV)radiation at 193 nm wavelength. In some embodiments, Hf is used toprovide good absorption of electron beam material and extreme UV (EUV)radiation. In some embodiments, one or more metal compositions includingTi, V, Mo, W, or combinations thereof are added to move an absorptionedge to longer wavelengths to provide sensitivity to ultraviolet (UV)radiation at 248 nm wavelength.

The organic ligands may be, for example, alkyls (e.g., methyl, ethyl,propyl, butyl, t-butyl, aryl (phenyl, benzyl)), alkenyls (e.g., vinyl,allyl), and carboxylates (e.g., acetate, propanoate, butanoatebenzoate). A ratio of concentration of the organic ligands toconcentration of the metal oxo-hydroxo cations in the precursor solutionis between about 0.25 and about 4 in one example, and between about 0.5and about 3.5 in another example, between about 0.75 and about 3 inanother example, and between about 1 and about 2.75 in other examples. Aperson of ordinary skill in the art will recognize that additionalranges of organic ligand concentrations within the explicit ranges aboveare contemplated and are within the present disclosure.

The organic solvent may be alcohols, esters, or combinations thereof. Insome embodiments, the organic solvent includes aromatic compounds (e.g.,xylenes, toluene), esters (propylene glycol monomethyl ether acetate,ethyl acetate, ethyl lactate), alcohols (e.g., 4-methyl-2-pentanol,1-butanol, anisole), ketones (e.g., methyl ethyl ketone), and the like.

In some embodiments, the deposited photoresist layer 308 has a thicknessof between about 1 nm and about 1 μm, for example, between about 8 nmand about 13 nm.

At operation 250, the photoresist layer 308 is exposed to radiationaccording to a selected pattern including features, such as trenches,vias, openings, and the like, with desired critical dimensions andprofiles to be formed in the film stack 302, as depicted in FIG. 3D. Theselected pattern is transferred to a corresponding pattern or latentimage in the photoresist layer 308 with irradiated areas andun-irradiated areas. When exposed to radiation, the photoresist layer308 absorbs radiation that results in energy that breaks the bondsbetween the metal and the organic ligands (i.e., metal carbon (M-C)ligand bonds and/or metal carboxylate (M-O₂C) ligand bonds) within theirradiated areas of the photoresist layer 308. This breakage of thebonds may lead to a composition change in the irradiated areas of thephotoresist layer 308 through formation of metal hydroxide (M-OH) ligandbonds or through condensation to form metal-oxygen (M-O-M) ligandsbonds.

With the absorption of a sufficient amount of radiation, there is acontrast of material properties between the irradiated areas of thephotoresist layer 308 without or substantially without the organicligands and the un-irradiated areas of the photoresist layer 308 withthe organic ligands intact. For example, the un-irradiated areas of thephotoresist layer 308 having the organic ligands are relativelyhydrophobic, and the irradiated areas of the photoresist layer 308 nothaving the organic ligands are less hydrophobic (i.e., more hydrophilic)than the un-irradiated areas of the photoresist layer 308. Using thiscontrast, the photoresist layer 308 may provide positive tone patterning(in which the irradiated areas become soluble to a developer agent) andnegative tone patterning (in which the irradiated areas become insolubleto a developer agent) with suitable developer agents.

The radiation may be electromagnetic radiation, an electron beam, orother suitable radiation. Radiation may be directed to the photoresistlayer 308 through a mask 310 or a radiation beam may be controllablyscanned across the photoresist layer 308. Electromagnetic radiation mayhave a desired wavelength or range of wavelengths, such as visibleradiation, ultraviolet (UV) radiation (between 100 nm and 400 nm,including extreme ultraviolet (EUV) between 10 nm and 121 nm and farultraviolet (FUV) between 122 nm and 200 nm), or x-ray radiation (softx-rays between 0.1 nm and 10 nm), depending on desired spatialresolution of patterning the underlying film stack 302. A higherresolution pattern may be achieved with shorter wavelength radiation,such as ultraviolet radiation, x-ray radiation, or an electron beam. Forexample, EUV radiation generated from a Xe or Sn plasma source excitedusing high energy lasers or discharge pulses may be used for lithographyat 13.5 nm.

In some embodiments, the contrast may be enhanced by a post-irradiationheat treatment.

At operation 260, the photoresist layer 308 is developed to pattern thephotoresist layer 308 according to the selected pattern, as depicted inFIG. 3E. The patterned photoresist layer 308A defines openings 312 thatexpose a surface 314 of the underlying hardmask layer 306 for etching.

A developer agent for developing the irradiated photoresist layer 308and removing the un-irradiated areas of the photoresist layer 308 (i.e.,negative tone patterning) to form a patterned photoresist layer 308A mayinclude an organic solvent, such as the solvents used in the precursorsolutions. In some embodiments, suitable developer agents includearomatic compounds (e.g., benzene, xylenes, toluene), esters (e.g.,propylene glycol monomethyl ester acetate, ethyl acetate, ethyl lactate,n-butyl acetate, butyrolactone), alcohols (e.g., 4-methyl-2-pentanol,1-butanol, isopropanol, anisole), ketones (e.g., methyl ethyl ketone,acetone, cyclohexanone), ethers (e.g., tetrahydrofuran, dioxane) and thelike. The development is performed for about 5 seconds to about 30minutes in one example, from about 8 seconds to about 15 minutes inanother example, and from about 10 seconds to about 10 minutes.

In some embodiments, the developer agent may include additionalcompositions to facilitate the development process, for example,improving the contrast, sensitivity and line width roughness, andinhibiting formation and precipitation of metal oxide particles.Suitable additives include, for example, dissolved salts with cationsselected from the group consisting of ammonium, d-block metal cations(hafnium, zirconium, lanthanum, or the like), f-block metal cations(cerium, lutetium or the like), p-block metal cations (aluminum, tin, orthe like), alkali metals (lithium, sodium, potassium or the like), andcombinations thereof, and with anions selected from the group consistingof fluoride, chloride, bromide, iodide, nitrate, sulfate, phosphate,silicate, borate, peroxide, butoxide, formate,ethylenediamine-tetraacetic acid (EDTA), tungstate, molybdate, or thelike and combinations thereof. Other potentially useful additivesinclude, for example, molecular chelating agents, such as polyamines,alcohol amines, amino acids, or combinations thereof. If the optionaladditives are present, the developer agent may include no more thanabout 10 weight percent additive in one example, and no more than about5 weight percent additive in another example. A person of ordinary skillin the art will recognize that additional ranges of additiveconcentrations within the explicit ranges above are contemplated and arewithin the present disclosure.

The developer agent may be applied to the irradiated photoresist layer308 using a spin-on-coating process, a spray coating process, or othersuitable coating processes. In some embodiments, spin rinsing and/ordrying may be performed to complete the development process. Suitablerinsing solutions include ultrapure water, methyl alcohol, ethylalcohol, propyl alcohol, and combinations thereof.

In some embodiments, the patterned photoresist layer 308A may be treatedto further condense the material and to further dehydrate the material.In some embodiments, the patterned photoresist layer 308A may be heatedto a temperature of between about 100° C. and about 600° C. in oneexample, between about 175° C. and about 500° C. in another example, andbetween about 200° C. and about 400° C. in other examples. The heatingmay be performed for at least about 1 minute in one example, for about 2minutes to about 1 hour in another example, and for between about 2.5minutes and about 25 minutes in other examples. The heating may beperformed in air, vacuum, or an inert gas ambient, such as Ar or N₂. Aperson of ordinary skill in the art will recognize that additionalranges of temperatures and time for the heat treatment within theexplicit ranges above are contemplated and are within the presentdisclosure.

In some embodiments, adjacent linear segments of neighboring structurescan have an average pitch of no more than about 60 nm, in someembodiments no more than about 50 nm and in further embodiments no morethan about 40 nm.

At operation 270, a passivation layer 316 is formed selectively on thepatterned photoresist layer 308A prior to etching of the hardmask layer306, as depicted in FIG. 3F. The passivation layer 316 may be formed ofcarbon-containing material by supplying a deposition gas mixture on thepatterned photoresist layer in a PVD chamber, or in-situ in an etchingchamber. In the embodiments described herein, the passivation layer 316is predominantly formed on a top surface 318 of the patternedphotoresist layer 308A, rather than sidewalls 320 of the patternedphotoresist layer 308A or the exposed surface 314 of the hardmask layer306. Thus, profile (e.g., dimensions and geometries) of the openings 312defined by the patterned photoresist layer 308A are maintained unchangedso as to facilitate transfer of the openings 312 to the hardmask layer306 without profile alternation.

While not intending to be bound by theory, it is believed that carbonatoms are bonded to the top surface 318 (i.e., the irradiated areas) ofthe photoresist layer 306 having the metal hydroxide (M-OH) ligand bondsand metal-oxygen (M-O-M) ligand bonds due to the breakage of the bondsbetween the metal and the organic ligands (i.e., metal carbon (M-C)ligand bonds and/or metal carboxylate (M-O₂C) ligand bonds). Sidewalls320 of the patterned photoresist layer 308A maintain the composition ofthe un-irradiated photoresist layer 308 having the organic ligandsintact, and thus do not contain the metal hydroxide (M-OH) ligand bondsand metal-oxygen (M-O-M) ligand bonds to which carbon atoms can bebonded. The exposed surface 314 of the hardmask layer 306 also does notcontain the metal hydroxide (M-OH) ligand bonds and metal-oxygen (M-O-M)ligand bonds, and thus carbon atoms are not bonded to the exposedsurface 314 of the hardmask layer 306.

In one or more embodiments, the deposition gas mixture includes acarbon-containing gas, such as CO gas or CH₄ gas. As described above,the hardmask layer 306 is formed of a material-containing metalelements, such as tin (Sn), and the photoresist layer 308 is also formedof a material containing metal elements, such as tin (Sn), leading topoor etch selectivity between the hardmask layer 306 and the photoresistlayer 308. Thus, if the hardmask layer 306 having the photoresist layer308 disposed thereon is etched, control of profile of openings etched inthe hardmask layer 306 may be inaccurate, eventually leading to devicefailure. Having the passivation layer 316 disposed thereon, thepatterned photoresist layer 308B may have higher etching selectivityfrom the hardmask layer 306, leading to higher accuracy control ofprofile of openings etched in the hardmask layer 306.

At operation 280, the hardmask layer 306 is etched to transfer theopenings 312 of the patterned photoresist layer 308A to the hardmasklayer 306, as depicted in FIG. 3G. The patterned hard mask layer 306Adefines openings 322 that exposes a surface 324 of the underlying BARClayer 304 for etching. In one or more examples, the etching process atoperation 280 is performed by supplying an etching gas mixture into theprocessing chamber 100 while maintaining a temperature of the substratesupport pedestal assembly 148 between room temperature (e.g., about 23°C.) and up to about 150° C.

In some examples, the etching gas mixture includes at least onehalogen-containing gas. The halogen-containing gas may include afluorine-containing gas, a chlorine-containing gas, or abromide-containing gas. Suitable examples of the halogen-containing gasinclude SF₆, SiCl₄, Si₂Cl₆, NF₃, HBr, Br₂, CHF₃, CH₂F₂, CF₄, C₂F, C₄F₆,C₃F₈, HCl, C₄F₈, Cl₂, HF, CCl₄, CHCl₃, CH₂Cl₂, and CH₃Cl. In someexamples, silicon-containing gas may also be supplied in the etching gasmixture. Suitable examples of the silicon-containing gas include SiCl₄,Si₂Cl₆, SiH₄, Si₂H₆, and the like. Furthermore, particularly, examplesof the chlorine-containing gas include HCl, Cl₂, CCl₄, CHCl₃, CH₂Cl₂,CH₃Cl, SiCl₄, Si₂Cl₆, and the like, and examples of thebromide-containing gas include HBr, Br₂, and the like. A reacting gas,such as an oxygen-containing gas or a nitrogen-containing gas, forexample, O₂, N₂, N₂O, NO₂, O₃, H₂O, or the like may also be supplied inthe etching gas mixture as needed.

In one or more examples, the halogen-containing gas used to etch thehardmask layer 306 comprises a chlorine-containing gas or abromide-containing gas. While supplying the etching gas mixture into theprocessing chamber, an inert gas may be optionally supplied into theetching gas mixture to assist the profile control as needed. Examples ofthe inert gas supplied in the gas mixture include Ar, He, Ne, Kr, Xe, orthe like. In one particular example, the etching gas mixture utilized toetch the hardmask layer 306, such as a metal-containing material (e.g.,a Sn/SnO/SnSiO layer), includes HBr, Cl₂, Ar, He, or combinationsthereof.

During etching, the chamber pressure of the etching gas mixture is alsoregulated. In one or more embodiments, a process pressure in the plasmaprocessing chamber is regulated between about 2 mTorr to about 100mTorr, for example, at about 3 mTorr and 20 Torr, such as about 6 mTorr.RF source or bias power may be applied to maintain a plasma formed froma continuous mode or a pulsed mode as needed in presence of the etchinggas mixture. For example, an RF power source with a frequency of about13.56 MHz may be applied at an energy level of between about 200 wattsto about 1,000 watts, such as about 500 watts, to an inductively coupledantenna source to maintain a plasma inside the etch chamber. Inaddition, an RF bias power, with a frequency of between about 2 MHz andabout 13.56 MHz, may be applied less than 500 watts, such as betweenabout 0 watts to about 450 watts, such as about 150 watts.

In one or more examples, the RF bias power and the RF power source maybe pulsed in the processing chamber 100 during the etching at operation280. The RF bias power and the RF power source may be synchronized ornon-synchronized pulsed into the processing chamber. In some examples,the RF bias power and the RF power source are non-synchronized pulsedinto the processing chamber. For example, the RF power source may bepulsed to the processing chamber prior to pulsing the RF bias power. Forexample, the RF bias power may be in pulse mode synchronized with the RFpower source or with a time delay with respect to the RF power source.In one or more examples, the RF power source and the RF bias power arepulsed between about 5% and about 75% of each duty cycle. Each dutycycle, for example between each time unit is between about 0.1millisecond (ms) and about 10 ms.

In one example of the etching gas mixture supplied at operation 280, theO₂ gas may be supplied into the chamber at a rate between about 0 sccmto about 50 sccm. The halogen-containing gas, such as HBr, may besupplied at a flow rate between about 25 sccm and about 250 sccm, suchas about 100 sccm.

At operation 290, the BARC layer 304 is etched to transfer the openings322 in the patterned hardmask 360A to the BARC layer 304, as depicted inFIG. 3H. The patterned BARC layer 304A defines openings 326 that exposesa surface 328 of the underlying film stack 302. The etching gas mixtureutilized to etch the BARC layer 304 at operation 290 may be the same asthe etching gas mixture utilized to etch the hardmask layer 306 atoperation 280. Alternatively, the etching gas mixture utilized to etchthe BARC layer 304 at operation 290 may be different from the etchinggas mixture utilized to etch the hardmask layer 306 at operation 280. Inone or more examples, the etching gas mixture utilized to etch the BARClayer 304 at operation 290 may include a chlorine-containing gas, suchas HCl or Cl₂ gas.

After the openings 326 are formed in the BARC layer 304, a de-scum or astrip process may be performed to remove the remaining passivation layer316, if any, as shown in FIG. 3I. It is noted that further etchingprocess or patterning process may be performed to continue transferringthe openings 326 into the film stack 302 and form the selected patternincluding features, such as trenches, vias, openings, and the like, withdesired critical dimensions and profiles within the film stack 302.

In the embodiments described herein, the methods are provided forforming a metal-containing photoresist layer having a carbon-containingpassivation layer selectively disposed thereon that has a high etchselectivity from an underlying metal-containing hardmask layer, leadingto higher accuracy control of profile of openings etched in the hardmasklayer. Thus, lithographic exposure accuracy, such as high resolution,low energy dose, good photoresist profile control and low line edgeroughness may be enhanced.

While the foregoing is directed to embodiments of the disclosure, otherand further embodiments may be devised without departing from the basicscope thereof, and the scope thereof is determined by the claims thatfollow. All documents described herein are incorporated by referenceherein, including any priority documents and/or testing procedures tothe extent they are not inconsistent with this text. As is apparent fromthe foregoing general description and the specific embodiments, whileforms of the present disclosure have been illustrated and described,various modifications can be made without departing from the spirit andscope of the present disclosure. Accordingly, it is not intended thatthe present disclosure be limited thereby. Likewise, the term“comprising” is considered synonymous with the term “including” forpurposes of United States law. Likewise whenever a composition, anelement or a group of elements is preceded with the transitional phrase“comprising”, it is understood that we also contemplate the samecomposition or group of elements with transitional phrases “consistingessentially of,” “consisting of”, “selected from the group of consistingof,” or “is” preceding the recitation of the composition, element, orelements and vice versa.

Certain embodiments and features have been described using a set ofnumerical upper limits and a set of numerical lower limits. It should beappreciated that ranges including the combination of any two values,e.g., the combination of any lower value with any upper value, thecombination of any two lower values, and/or the combination of any twoupper values are contemplated unless otherwise indicated. Certain lowerlimits, upper limits and ranges appear in one or more claims below.

What is claimed is:
 1. A method for etching a hardmask layer,comprising: forming a photoresist layer comprising an organometallicmaterial on a hardmask layer comprising a metal-containing material;exposing the photoresist layer to ultraviolet radiation through a maskhaving a selected pattern; removing un-irradiated areas of thephotoresist layer to pattern the photoresist layer; forming apassivation layer comprising a carbon-containing material selectively ona top surface of the patterned photoresist layer; and etching thehardmask layer exposed by the patterned photoresist layer having thepassivation layer formed thereon.
 2. The method of claim 1, wherein theorganometallic material comprises one or more metal elements and organicligands.
 3. The method of claim 2, wherein the one or more metalelements comprise tin (Sn).
 4. The method of claim 2, wherein theorganic ligands are selected from the group consisting of alkyls,alkenyls, and carboxylates.
 5. The method of claim 1, wherein theforming of the passivation layer comprises: supplying deposition gascomprising a gas selected from the group consisting of CO and CH₄ ontothe patterned photoresist layer.
 6. A method for etching a film stack,comprising: forming a bottom anti-reflective coating layer on a filmstack; forming a hardmask layer comprising a metal-containing materialon the bottom anti-reflective coating layer; forming a photoresist layercomprising an organometallic material on the hardmask layer; exposingthe photoresist layer to ultraviolet radiation through a mask having aselected pattern; removing un-irradiated areas of the photoresist layerto pattern the photoresist layer; forming a passivation layer comprisinga carbon-containing material selectively on a top surface of thepatterned photoresist layer; etching the hardmask layer exposed by thepatterned photoresist layer having the passivation layer formed thereonto pattern the hardmask layer; etching the bottom anti-reflectivecoating layer exposed by the patterned hardmask layer to pattern thebottom anti-reflective coating layer; and etching the film stack exposedby the patterned bottom anti-reflective coating layer.
 7. The method ofclaim 6, wherein the organometallic material comprises one or more metalelements and organic ligands.
 8. The method of claim 7, wherein the oneor more metal elements comprise tin (Sn).
 9. The method of claim 7,wherein the organic ligands are selected from the group consisting ofalkyls, alkenyls, and carboxylates.
 10. The method of claim 6, whereinthe forming of the passivation layer comprises: supplying deposition gascomprising a gas selected from the group consisting of CO and CH₄ ontothe patterned photoresist layer.
 11. The method of claim 6, wherein themetal-containing material of the hardmask layer comprises tin (Sn). 12.The method of claim 11, wherein the metal-containing material of thehardmask layer is selected from the group consisting of tin oxide (SnO),tin silicon oxide (SnSiO), tantalum oxide (TaO), indium tin oxide(InSnO), indium gallium zinc oxide (IGZO), and any combination thereof.13. The method of claim 6, wherein the bottom anti-reflective coatinglayer comprises a carbon-containing material.
 14. A method forselectively forming a passivation layer on a patterned photoresistlayer, comprising: exposing a photoresist layer comprising anorganometallic material to ultraviolet radiation through a mask;removing un-irradiated areas of the photoresist layer; and forming apassivation layer comprising a carbon-containing material selectively ona top surface of the photoresist layer.
 15. The method of claim 14,wherein the organometallic material comprises one or more metal elementsand organic ligands.
 16. The method of claim 15, wherein the one or moremetal elements comprise tin (Sn).
 17. The method of claim 15, whereinthe one or more metal elements are selected from the group consisting oftin (Sn), antimony (Sb), and indium (In), and any combination thereof.18. The method of claim 15, wherein the organic ligands are selectedfrom the group consisting of alkyls, alkenyls, and carboxylates.
 19. Themethod of claim 14, further comprising: heating the patternedphotoresist layer.
 20. The method of claim 14, wherein the forming ofthe passivation layer comprises: supplying deposition gas comprising agas selected from the group consisting of CO and CH₄ onto the patternedphotoresist layer.